TITLE:
Assessment of Topographic Wetness Index for Flood-Prone Zone Delineation in the Yola Sub-Basin, Nigeria, Using High-Resolution DEM
AUTHORS:
Bijida Adamu Malik, Saminu Ahmed, Rabia Lawal Batagarawa, Haruna Garba
KEYWORDS:
Topographic Wetness Index (TWI), Digital Elevation Model (DEM), Flood Vulnerability, Geomorphometry, GIS, Yola Sub-Basin, Nigeria
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.4,
March
31,
2026
ABSTRACT: The Yola Sub-Basin, situated in Nigeria’s Upper Benue Trough, is increasingly threatened by floods due to changing climatic conditions, adversely affecting agriculture, infrastructure, and communities. This study aims to enhance flood mitigation strategies through accurate identification of water accumulation zones using the Topographic Wetness Index (TWI), a valuable geomorphometric tool. We employed an advanced GIS-based methodology to compute and validate the TWI for predicting surface saturation and water accumulation potential. A 30-meter resolution Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) was processed with ArcGIS Pro 3.1 and Python scripting, involving hydrological conditioning, flow direction derivation via the D8 algorithm, and slope gradient calculation. Results demonstrated TWI values spanning from 2.5 in steep uplands to over 18 in low-lying floodplains, categorized into five susceptibility levels. Notably, high to very high TWI zones, constituting approximately 28% of the sub-basin, exhibited a strong correlation (Kappa = 0.85) with significant flood events (2022-2023) and established agricultural wetlands (Fadamas). These findings robustly validate the TWI’s effectiveness for flood hazard assessment and underscore its importance in sustainable land-use planning in the region.